Spotify has not turned to shit. It might happen in future but isn't happening right now and they're showing no signs of letting it happen.
If and when Spotify does turn to shit I'll move on: I'll download my playlists and fetch every track via yt-dlp, deemix, et al., manage tags and cover art with musicbrainz et al, use AI to create tools that generate playlists that I can sync to my devices. I'll carry it with me on all my devices. I anticipate the library being around 30-60gb, not that much these days. But man is all that a ton of work.
My world-view is: I use great stuff while it's great, and hedge against it turning to shit by having an escape plan. But to sit around not using something great because there's a chance it might turn to shit in the future, is missing out on how good the thing is right now.